METAL PROPERTIES, CHAR, USES, AND CODES - OD1643 - LESSON 1/TASK 1
the normalized and annealed condition. During welding, the weld zone
will become hardened if cooled rapidly and must be stress-relieved
after welding.
(f) High-Carbon Steels.
These steels are used for the
manufacture of drills, taps, dies, springs, and for those machine
tools and handtools that are heat treated after fabrication to
develop the hard structure necessary to withstand high shear stress
and wear.
High-carbon steels are manufactured in bar, sheet, and
wire forms, and in the annealed or normalized and annealed condition,
in order to be suitable for machining before heat treatment.
These
steels are difficult to weld because of the hardening effect of heat
at the welded joint.
(g) Tool Steels.
These steels are used in the manufacture of
chisels, shear blades, cutters, large taps, wood-turning tools,
blacksmith's tools, razors, and other similar parts where high
hardness is required to maintain a sharp cutting edge.
They are
relatively difficult to weld due to the high carbon content.
(4) Cast Steel. Generally, welding is difficult on steel castings
containing over 0.23 percent carbon and 0.2 percent silicon.
Alloy
steel castings containing nickel, molybdenum, or a combination of
these metals, are readily welded if the carbon content is low. Those
containing chromium or
vanadium are more difficult to weld
satisfactorily.
Since manganese steel is nearly always used in the
form of castings, and is difficult to weld, it is also mentioned in
this paragraph. Its high resistance to abrasion is its most valuable
property.
(5) Steel Forgings. Steel forgings may be made of carbon or alloy
steels.
Alloy steel forgings are harder and more brittle than low
carbon steels. The surface of steel forgings is smooth. Where the
surface of drop forgings has not been finished, there will be
evidence of the fin that results from metal squeezed out between two
forging dies.
This fin is ordinarily removed by the trimming dies,
but enough of the sheared surface remains for identification.
All
forgings are covered with reddish-brown or black scale, unless they
have been purposely cleaned.
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